ES2899656T3 - Use of layered structures in wind power plants - Google Patents

Abstract

Use of a laminated structure in the production of rotor blades for wind power plants, wherein the laminated structure has the following layers: a) a central separating layer b) possibly a gel coating layer c) a layer of fibers treated with plastic material d) optionally a separating layer e) a layer of fibers provided with plastic material f) optionally a sheet of plastic material characterized in that polyurethane is used as the plastic material, which is injected in the evacuated layered structure already prepared as a reaction mixture formed by isocyanate components and compounds with at least two hydrogen atoms reactive towards isocyanates.

Description

DESCRIPTION

Use of layered structures in wind power plants

The present invention relates to the use of laminated structures in the manufacture of rotor blades for wind power plants, as well as rotor blades for wind power plants.

The energy obtained from wind power is becoming increasingly important, so that wind power plants, in particular rotor blades and their manufacture are the object of intensive study and development. In this connection, a main focus of attention is on the quality of the manufactured rotor blades, as well as on economically favorable manufacturing. Until now known rotor blades for wind power plants are made of fiber-reinforced plastic materials based on resins as matrix material, such as, for example, polyester resins (UP), vinyl ester resins (VE), resins epoxy (EP). The manufacture of the blades is mainly carried out in such a way that respectively a lower half and an upper half of the blade are manufactured as one piece. Subsequently, these two halves are superimposed and adhesively joined. As reinforcement, braces or straps are included in the adhesive joint.

In the manufacture of the two blade halves, the fiber composite materials are first manufactured, which must be solidified and hardened. The curing process is time consuming and disadvantageous to the speed with which the overall manufacturing process can be carried out. Rotor blades for wind power plants made from the aforementioned resins are usually manufactured by hand rolling, hand rolling with the support of prepreg technology, by winding processes or through a vacuum-supported infusion process. In manual lamination, a mold is first prepared by applying a release medium and, if necessary, a gel film, to the surface of the mold. Fiberglass fabrics with unidirectional or biaxial orientation were then successively placed inside the mold. The resin is then applied to the fabric and manually integrated into the fabric using rollers. This stage can be repeated as many times as necessary. Additionally, straps can be integrated as reinforcing material or other components, such as, for example, lightning protection devices. A so-called spacer layer, usually made of balsa wood, polyvinylchloride (PVC) or polyurethane (PUR) foam, is applied on top of this first fiberglass-reinforced layer, and a second fiberglass-reinforced layer is applied analogously. Although this procedure has the advantage that investments in machinery are kept low and error recognition and correction possibilities are simple, this type of manufacturing is, however, too labor intensive, so that the costs of the procedure are very high and the long manufacturing times result in more errors and a high expense for quality assurance.

The manual lamination process supported by prepreg technology is carried out in a similar way to the simple manual lamination process. In this regard, however, so-called prepregs (prefabricated resin-impregnated fiberglass mats) are made outside the mold and subsequently placed in the rotor blade mould. While partial automation for prepreg fabrication, compared to simple manual lamination, leads to improved quality consistency in rotor fabrication, worker protection from highly volatile compounds contained in liquid resin blends means a substantial expense (job site safety, etc.).

EP 2 148087 A discloses the use of a polyurethane foam in conjunction with a "line support" for cables inside the turbine, but not in the rotor blade. The use of polyurethane powders for the preparation of prepreg composite materials for rotor blades is not described in previously published WO 2010/108701 A. DE 10150247 discloses the outer covering of a body around which fluids flow, which contains a polyurethane layer as a thin outer layer (possibly profiled), which is laminated to an equally thin fabric layer. In this case, the polyurethane and the fabric layer are not combined to form a fiber reinforced plastic.

In the resin injection process (also known as "Resin Transfer Molding" or "Vacuum Supported Resin Transfer Molding" (VA RTM) or the " SCRIMP Process” (“Seeman C omposites R esin j nfusion M olding P rocess” or “Seemann Composites Resin Infusion Molding Process”), the molds are prepared by applying a separating medium and possibly a layer of gel coat. The dry fiber mats are then placed in the mold according to an exact manufacturing plan. The first layer placed afterwards will be the layer facing the outside of the rotor blade. Spacer materials are then placed, after which fiber mats are laid again, which then form the inner layer of the finished rotor half or half-rotor shell, respectively With a vacuum-resistant sheet, the entire mold is then hermetically sealed. The thus prepared mold is then de-aired from the fiber mats and spacer materials, before the resin is injected into the mold at different places (gap between sheet and mold). Like the two procedures mentioned above, this procedure also has the disadvantage that the hardening time required until the piece can be demoulded is very long, up to 12 hours, so the productivity of the facilities is strongly limited.

Therefore, the object of the present invention was to provide rotor blades that do not have the disadvantages previously mentioned and which can also be manufactured in an economically favorable manner in a shorter time.

This objective has surprisingly been achieved because the rotor blades are made of polyurethane as the plastic material used instead of the above-mentioned resins. In particular in the outer layer of the rotor blade, according to the present invention polyurethane is used as the plastic material; The fibrous layers inserted in the outer layer are loaded with this material.

The object of the invention is a process for the manufacture of rotor blades for wind power plants, which have an outer layer that is formed at least partially by a stratified structure with the following layers:

a) a central separating layer

b) if necessary, a layer of gel coating

c) a layer of fibers treated with plastic material

d) if necessary, a separating layer

e) a layer of fibers provided with plastic material

f) if necessary, a sheet of plastic material

where the reaction mixture formed by isocyanate components and compounds with at least two reactive hydrogen atoms against isocyanates is injected into the already prepared evacuated layered structure, and

A further object of the invention are rotor blades for wind power plants, which are produced by the method according to the invention.

An additional object of the invention is the use of a layered structure in the case of manufacturing rotor blades for wind power plants according to the method according to the invention, where the layered structure has the following layers:

a) a central separating layer

b) if necessary, a layer of gel coating

c) a layer of fibers treated with plastic material

d) if necessary, a separating layer

e) a layer of fibers provided with plastic material

f) if necessary, a sheet of plastic material

and is characterized in that polyurethane is used as plastic material, which is injected into the already prepared evacuated layer structure as a reaction mixture consisting of isocyanate components and compounds with at least two isocyanate-reactive hydrogen atoms.

Silicone- or wax-containing release agents are preferably used for the central separating layer. These are known from the literature.

The gel coat layer preferably consists of polyurethane resins, epoxy resins, unsaturated polyester or vinyl resins.

As fiber layer, it is preferable to use randomly oriented fiber structures, fabrics and fabrics made of chopped or ground glass fiber, glass fibers or mineral fibers, as well as fiber mats, fiber fleeces and fiber mesh fabrics based on polymer, mineral, carbon, glass or aramid fibers and mixtures thereof, particularly preferably glass fiber mats or glass fiber fleeces. Foams made of plastic, wood or metal can preferably be used as the spacer layer.

The plastic foil optionally used in the production of the rotor blade can remain as a layer in the casing or can be removed during demoulding of the respective rotor blade half. It serves in particular to seal the mold shell, which is provided with the previously mentioned layers, during the manufacturing process, before filling with the liquid resin mixture.

Polyurethane is used as plastic material. Polyurethanes can be obtained by reacting polyisocyanates with compounds containing at least two hydrogen atoms that are reactive towards isocyanates. The reaction mixture consisting of isocyanate components and compounds with at least two isocyanate-reactive hydrogen atoms is injected into the already prepared evacuated layer structure.

Compounds with at least two hydrogen atoms that are reactive towards isocyanates are generally considered to be those that carry two or more reactive groups in the molecule, such as, for example, OH groups, SH groups, NH groups, NH2 groups. and acidic CH groups. Preference is given to using polyether polyols and/or polyester polyols, particularly preferably polyether polyols. The polyol formulation preferably contains as polyols those having an OH number of 200 to 1,830 mg KOH/g, preferably 300 to 1,000 mg KOH/g, and particularly preferably 350 to 500 mg KOH/g. The viscosity of polyols is preferably < 800 mPas (at 25 °C). The polyols preferably contain at least 60%, preferably at least 80%, secondary OH groups and more preferably 90% secondary OH groups. Polyether polyols based on polypropylene oxide are particularly preferred.

The commonly used aliphatic, cycloaliphatic and, in particular, aromatic di- and/or polyisocyanates are used as polyisocyanate component. Examples of such suitable polyisocyanates are 1,4-butylene diisocyanate, 1,5-pentadiisocyanate, 1,6-hexamethylene diisocyanate (h Di), isophorone diisocyanate (IPDI), 2,2,4- and/or 2,4,4-trimethylhexamethylene diisocyanate, bis(4,4'-isocyanatocyclohexyl)methane or its mixtures with the common isomers, 1,4-cyclohexylene diisocyanate, 1,4-phenylenediisocyanate, 2,4- and/or 2,6-toluylene diisocyanate (TDI), 1,5- naphthylene diisocyanate, 2,2'-and/or 2,4'- and/or 4,4'-diphenylmethane diisocyanate (MDI) and/or higher homologs (pMDI) thereof, 1,3- and/or 1,4- bis-(2-isocyanato-prop-2-yl)-benzol (TMXDI), 1,3-bis-(isocyanatomethyl)benzol (XDI). Diphenylmethanediisocyanate (MDI) is preferably used as isocyanate, in particular mixtures of diphenylmethanediisocyanate and polyphenylenepolymethylenepolyisocyanate (pMDI). The mixtures of diphenylmethane diisocyanate and polyphenylene polymethylene polyisocyanate (pMDI) have a monomer content preferably between 40 and 100% by weight, more preferably between 50 and 90% by weight, and even more preferably between 60 and 80% by weight. The NCO content of the polyisocyanate used should preferably be above 25% by weight, more preferably above 30% by weight and even more preferably above 31.4% by weight. The MDI used should preferably have a combined content of 2,2'-diphenylmethane diisocyanate and 2,4'-diphenylmethane diisocyanate of at least 3% by weight, preferably at least 20% by weight, particularly preferably at least less than 40% by weight. The viscosity of the isocyanate should preferably be <250 mPas (at 25°C), more preferably <100 mPas (at 25°C) and even more preferably <50 mPas (at 25°C).

The polyurethane reaction mixture, in addition to the known reactive components, additives and addition agents, may preferably include fillers, such as carbon nanotubules, barium sulfate, titanium dioxide, short glass fibers or natural minerals in the form of fibers. or platelets, eg volastonite or muscovite. Defoamers, catalysts and latent catalysts are preferably used as additives and addition agents. Other known additives and adding agents can be used as needed.

Suitable polyurethane systems are in particular those that are transparent. Since a low viscosity is required for uniform mold filling in the production of larger molded parts, polyurethane systems with a viscosity of < 5000 mPas (at 25 °C; 30 minutes after mixing) are particularly suitable. of the components), preferably <2000 mPas, particularly preferably <1000 mPas. Preferably, the conversion ratio between the isocyanate component and the compounds with at least two isocyanate-reactive hydrogen atoms is selected such that the ratio of the number of isocyanate groups to the number of isocyanate groups in the reaction mixture of reactive groups towards isocyanate is between 0.9 and 1.5, preferably between 1.0 and 1.2, and even more preferably between 1.02 and 1.1.

In a preferred embodiment, the reaction mixture formed by the isocyanate component and compounds with at least two reactive hydrogen atoms against isocyanates is injected at a temperature between 20 and 80 °C, more preferably between 25 and 40°C.

After the filling of the reaction mixture, the hardening of the polyurethane can be accelerated by heating the mold. In a preferred embodiment, the injected reaction mixture consisting of the isocyanate component and the other compounds with at least two isocyanate-reactive hydrogen atoms is hardened at a temperature between 40 and 160 °C, preferably between 60 and 120 °C, more preferably between 70 and 90 °C.

The present invention is described in more detail below based on the following examples.

examples

Moldings (plates) of different polyurethane systems were made and compared with a standard epoxy resin system. The size of the plates was 17 cm * 17 cm with a thickness of 4 mm.

The demould time is that time after which the PUR sample bodies can be removed from the plate mold manually without deformation.

The viscosity was determined 30 minutes after the components were mixed, since for the manufacture of larger molded parts, a low viscosity is required for a uniform filling of the mold for a certain time.

Example 1

70 g of Baygal® K 55 (polyether polyol from Bayer MaterialScience AG; OH number: 385 ± 15 mg KOH/g; viscosity at 25 °C: 600 ± 50 mPas) were stirred with 65.3 g of Baymidur ® K 88 (product of the company Bayer MaterialScience AG; mixture of diphenylmethane diisocyanate and polyphenylene polymethylene polyisocyanate; content of NCO 31.5 ± 0.5% by weight; viscosity at 25 °C: 90 ± 20 mPas) at room temperature and degassed with negative pressure. The solution was poured into a plate mold and stored at room temperature for one hour. Afterwards, the sample was tempered at 80 °C. The gelation time was about 70 minutes and the demoulding time was two hours.

The test body had a hardness of 76 Shore D.

The viscosity at 25[deg.] C. was 1540 mPas 30 minutes after mixing the components.

Example 2

70 g of Baygal® K 55 (polyether polyol from Bayer MaterialScience AG; OH number: 385 ± 15 mg KOH/g; viscosity at 25 °C: 600 ± 50 mPas) were stirred with 63 g of Baymidur® VP .KU 3-5009 (Bayer MaterialScience AG; mixture of diphenylmethane diisocyanate and polyphenylene polymethylene polyisocyanate; NCO content 31.5 ± 33.5% by weight; viscosity at 25 °C: 15 - 30 mPas) at room temperature and degassed with negative pressure. The solution was poured into a plate mold and stored at room temperature for one hour. Afterwards, the sample was tempered at 80 °C. The demoulding time was two hours.

The test body had a hardness of 76 Shore D.

The viscosity at 25[deg.] C. was 974 mPas 30 minutes after mixing the components.

Comparative Example 3

180 g of infusion resin Larit RIM 135 (L-135i) (product of the company Lange+Ritter) were stirred with 60 g of hardener Larit RIMH 137 (product of the company Lange+Ritter) at room temperature and degassed under negative pressure. . The solution was poured into a plate mold and stored at room temperature for one hour. Afterwards, the sample was tempered at 80 °C. The demoulding time was twelve hours.

The test body had a hardness of 76 Shore D.

The polyurethane system could be demoulded significantly faster. The faster demolding time of the polyurethane system enables higher productivity, since the holding time of the molds can be considerably reduced and thus more moldings can be produced.

Claims (8)

1. Use of a laminated structure in the manufacture of rotor blades for wind power plants, wherein the laminated structure has the following layers: a) a central separating layer b) if necessary, a layer of gel coating c) a layer of fibers treated with plastic material d) if necessary, a separating layer e) a layer of fibers provided with plastic material f) if necessary, a sheet of plastic material characterized in that polyurethane is used as the plastic material, which is injected into the already prepared evacuated layered structure as a reaction mixture consisting of isocyanate components and compounds with at least two isocyanate-reactive hydrogen atoms. 2. Process for the manufacture of rotor blades for wind power plants, which have an envelope that is composed at least partially of a stratified structure with the following layers: a) a central separating layer b) if necessary, a layer of gel coating c) a layer of fibers treated with plastic material d) if necessary, a separating layer e) a layer of fibers provided with plastic material f) if necessary, a sheet of plastic material, characterized in that the fiber layers are treated with a reaction mixture for the preparation of polyurethane as plastic material, wherein the reaction mixture consisting of isocyanate components and compounds with at least two isocyanate-reactive hydrogen atoms is injected in the evacuated layered structure already prepared as a reaction mixture. Process according to Claim 2, characterized in that the reaction mixture contains diphenylmethanediisocyanate and/or polyphenylenepolymethylenepolyisocyanate with an NCO content of more than 25% by weight as isocyanate. Process according to claim 2, characterized in that the reaction mixture as a compound with at least two isocyanate-reactive hydrogen atoms contains a polyether polyol in which at least 60% of the OH groups are secondary OH groups and have an OH value of 200 to 1830 mg KOH/g. Method according to claim 2, characterized in that the reaction mixture is applied inside the fiber layers at a temperature between 20 and 80 °C. 6. Process according to claim 2, characterized in that the reaction mixture is cured at a temperature between 40 and 160 °C. 7. Process according to claim 2, characterized in that the reaction mixture has a viscosity of <5000 mPas 30 minutes after mixing. 8. Rotor blades for wind power plants, manufactured according to a method according to claim 2.